In a variety of industrial situations, machines perform operations on workpieces too long and/or heavy for the machine to support by itself. For example, in the woodworking industry, when a long piece of lumber is passed through a planer or through a table saw, some type of supplemental support is often used. A variety of stands such as roller stands and roller tables are available to meet this need. However, these devices pose a number of problems.
One major problem addressed in prior art is the instability of most supplemental support devices in that they are frequently moved out of position by the workpiece. A number of inventions have dealt with this problem by developing extension supports which attach directly to the machine's work surface. Lehner, U.S. Pat. No. 1,864,840 in 1932, developed an adjustable extension stock support with both horizontal and vertical adjustments which attach directly to the machine's work surface. Skinner in U.S. Pat. No. 5,105,862, April 1992, patented an extension table mainly for a miter saw with an adjustable leg making it attachable to tools with different height or even to an adjustable-height surface. However, the leg, an adjustable telescoping leg, required manual adjustment.
A number of machines including the frame mounted planer, have work surfaces with adjustable-height. This creates an additional problem for extension tables. In order for the extension table to function properly, its height must continually be adjusted each time the work surface height is changed. To address this problem, a number of automatically adjusting extension tables are found in prior art. In 1926, Hallock, U.S. Pat. No. 1,583,879, patented an auxiliary supporting table which raised and lowered simultaneously with the planer bed. Hallock's design used wedge shaped members moved by a jack screw and extension rod to change the planer bed height and the extension table height simultaneously. In May 1989, Feyer received a patent, U.S. Pat. No. 4,830,876, for an automatically adjusting extension table used with a bench type planer, Feyer's design, like Hallock's, used moveable wedge shaped bodies, one siding under the other, to raise or lower the outer end of the extension table with the proximal end attached solidly to the planer bed.
Canfield, in U.S. Pat. No. 6,491,071, December 2002, disclosed a height adjustable extension table with proximal end rigidly attached to a height adjustable planer bed with the distal end being supported by a two part leg, hinged in the middle, and being pulled by a cable passing through a pulley to raise or lower the planer bed. While these cited examples provide methods for automatically adjusting the height of the extension table, all three require the table to be rigidly mounted to the machine. Both Feyer and Canfield require part of the apparatus to be attached to the floor or bench making the machine and extension table completely immobile.
The problem of mobility of shop equipment has become an issue of increasing importance. In recent years, frame mounted planers capable of heavy duty operation are mounted on a mobile base to allow the machine to be moved to a needed location or out of the way when not in use. In U.S. Pat. No. 5,255,724, October 1993, Butke addressed the need for extension tables to be attached only to the machine so mobility would not be decreased. He developed an extension table for joiners with both the extension table and supporting member attached only to the machine.
Another need addressed in prior art is the extension table being foldable or easily removed to facilitate storage. In U.S. Pat. No. 2,555,217, Young disclosed a foldable extension table which easily detaches using thumb screws. Kreitz, in U.S. Pat. No. 4,068,551, January 1978, revealed an extension table which is easily removed and folded for storage. Both Kreitz and Young developed extension tables mainly for power saws such as table saws and radial saws. While these extension tables provide for mobility and/or folding for storage, they lacked the ability to automatically adjust to changing height of the surface to which they were attached. Also, in the Butke, Young, and Krietz designs, the machine itself must completely support the weight of the extension table and workpiece.